In order to implement an ABACUS application problem specific classes have to be derived from the classes ABA_MASTER and ABA_SUB. ABACUS provides already some non-abstract classes derived from the classes ABA_CONSTRAINT and ABA_VARIABLE, but if there is application specific structure to be exploited, classes also have to be derived from ABA_VARIABLE and ABA_CONSTRAINT.
Some other classes are included in this section because they are base classes of the application base classes ABA_MASTER, ABA_SUB, ABA_CONSTRAINT and ABA_VARIABLE. The class ABA_ABACUSROOT is a base class of every class of the system. The class ABA_GLOBAL is a base class of the class ABA_MASTER. Common features of constraints and variables are embedded in the class ABA_CONVAR, from which the classes ABA_CONSTRAINT and ABA_VARIABLE are derived.